Existing cable termination systems for connecting a cable to an apparatus, two cables or two feeder cables with a tap are known in the art. A termination system typically includes, at a minimum, a cable or wire preferably having a coupling device, such as a metallic lug, an apparatus preferably having a terminal for connecting to the system, a stud (i.e., a pin type or threaded device inserted into the aperture of the metallic lug), mating devices (i.e., devices that couple to the stud to maintain the stud within the aperture of the metallic lug) and a housing (i.e., a device that encloses the cable/apparatus connection). According to the use of the termination system, it can further comprise a component and the like for making the system suitable for the specified use. For example, the component can be a specific plug, or it can be connected to another device, examples of which include a termination system, a transformer, switch and/or a switchgear.
According to a commonly known termination system, a metallic lug containing an aperture is attached to an end of a cable, which is then inserted into a bore entrance of a housing such that the end of the metallic lug containing the aperture enters the housing first. Typically, the aperture in the lug can be one of two “primary” varieties. The industry standard lug, which is also the oldest lug, contains a ⅝ in. through-aperture which is slightly large enough to allow passage of a threaded stud comprising ⅝ inch, at 11 threads per inch (⅝″-11), which is often used with an elbow and epoxy insulating plug, reducing tap well, connecting plug or a 200A dead break reducing tap plug. With the development of the “operable” products, which often use a 600 ampere-to-200 ampere load break reducing tap plug, it became necessary to marry the load break reducer to the 600 amp elbow. This was accomplished by increasing the standard lug aperture to a 15/16″-9 threaded aperture, which was the smallest thread size that would still allow passage of a ⅝″-11 threaded member. The prepared cable/lug assembly can be inserted into the cable entrance of the elbow, and the load break reducing tap plug could then be threaded into the lug. However, the threading process can create significant field problems.
Typically, a first mating device having a component, for example, a loadbreak reducing tap plug, or a dead break reducing tap plug having a deadbreak interface, etc is inserted into a second bore entrance of the housing. According to a method known in the art, the first mating device can be suitable for use with a device that can be electrically connected to the cable via the second mating device. The connection may incorporate additional components and may be performed in alternative configurations utilizing a variety of methods that are known in the art. The component of the first mating device can either include a stud, which is inserted into the aperture of the metallic lug or a cavity for receiving such a stud.
A second mating device, for example, a terminal affixed to the apparatus (e.g., bushing, transformer, high voltage switch, etc.) is then inserted into a third bore entrance. Similar to the first mating device, the second mating device can also include a stud or a cavity. When the terminal system is assembled, a conductive physical connection can be created between the metallic lug and the first and second mating devices.
If the component of the first mating device comprises a stud and the second mating device comprises a cavity, the stud can be inserted through the aperture of the metallic lug and into the cavity of the second mating device. The stud and metallic lug can engage either via complementing threaded portions or by sliding the bolt into the aperture of the metallic lug, which can result in the component of the first mating device and metallic lug to be electrically connected preferably via the face and sleeve of the lug. If the mating device is a load break tap plug, such as the Load Reducing Tap Plug (LRTP), the aperture of the lug can be threaded, thereby permitting a threading engagement between the lug and the load break reducing tap plug, which is performed initially with everything de-energized. Or, if the mating device is a Reducing Tap Plug (RTP), Reducing Tap Well (RTW) or Connecting Plug (CP), the stud can be slid through the aperture of the metallic lug into the cavity of the mating device to create an electrical connection. The respective first mating device can subsequently threadingly engage the second mating device.
Alternatively, if the component of the first mating device comprises a cavity and the second mating device comprises a stud, the assembly comprising the housing and the first mating device must be properly aligned and placed over the second mating device. However, because the assembly of the housing and the first mating device lacks a stud holding the metallic lug, the housing and the first mating device together, each element must be properly aligned and balanced to ensure proper insertion of the stud through the aperture of the metallic lug and into the cavity of the component of the first mating device. Alternatively, in accordance with the T OP II™ manufactured by Cooper Power Systems, the first mating device can include a threaded member having a threaded exterior as well as a threaded cavity. This threaded member can be threaded into the aperture of the metallic lug. Thereafter, the threaded stud of the second mating device can be inserted into and threadingly engaged with the threaded member.
Typically, the installer of the termination system must manually maneuver a bolt through the component of the first mating device, through the aperture of the metallic lug and into the cavity of the second mating device, and tighten the bolt using an instrument several feet long until the three elements are electrically connected. It is preferable for the instrument to be several feet long to maintain a sufficient distance between the installer and the termination system in order to protect the installer from potential harm. The bolt must be inserted in the proper direction and angle to properly hold the assembly in place, which can become a difficult task at a several feet distance. However, if the first mating device is an LRTP or T OP II™, it is already assembled into the lug aperture, and if the first mating device is an RTW, RTP, CP (Connecting Plug) or an insulating plug, such as a BIP, this tightening procedure would not be performed using a hot stick or a long instrument.
One potential problem that may arise is that if a sleeve of an LRTP or T OP II™ is threaded, it may cross thread with the threading in the metallic lug, thereby failing to create a secure and stable electrical connection. The installer may feel resistance from the cross threading and can assume that the resistance indicates a complete, secure connection. This problem is aggravated by the fact that the installer is performing the task blind, without being able to see the threading. Moreover, the lug, and therefore the thread in the lug, is of rather soft materials (aluminum and copper) and is easily cross-threaded. Additionally, proper alignment of the threads can be very difficult because of the weight of the cable. On top of the fact that the operation cannot be viewed and the weight of the cable, the lineman must force the load break reducing tap plug forward to overcome the rubber interference while trying to engage the thread, creating potential problems. Furthermore, the total thread engagement of the prior art is typically only a maximum of ½ inch, the width of the lug, rather than a more accepted engagement of 1½ times the diameter of the thread. Because of the very short thread length there is no room for a lead-in on the male portion to allow proper alignment.
Alternatively, if a product such as a connecting plug, reducing tap well, reducing tap plug, or insulating plug, which do not thread into the metallic lug is used, the installer must force the mating device into the elbow while simultaneously pushing the elbow onto the bushing or Connecting Plug, potentially creating difficulties during installation.
Another potential problem with the commonly known connectors and methods of connecting an electrical cable to an apparatus is the difficulty in connecting the cable and apparatus via separate components, for example, reducing tap plugs, connecting plugs, reducing tap wells, and the like. Typically, the components are independent from the connector housing and must be inserted into the second bore entrance and is connected to the housing by friction fit. According to whether or not the first mating device comprises a stud, different drawbacks are present.
Some other prior art termination systems utilize a connector housing and a separately molded mating device comprising a component having a threaded stud, such as the LRTP device shown in FIG. 2. The separately molded component includes a component guide portion for guiding and aligning the component into the aperture of the metallic lug, as well as a threaded portion for threadingly engaging the metallic lug, thereby pulling the separately molded mating device further into the second bore of the housing and holding it in position. More specifically, a cable assembly is inserted into the connector housing. Then, while holding the cable assembly in place, the separately molded component is inserted into a bore such that the component guide portion passes through the aperture of the metallic lug of the cable assembly, then the separately molded component is threadingly engaged with the metallic lug. Therefore, the three separate elements, the cable assembly, the housing and the separately molded component, which can be cumbersome and heavy, must be properly positioned and held in that position during this process.
The separately molded component further comprises two threading elements that engage each other, which pull the housing portion further into the second bore of the termination system housing when the threaded portion is prevented from threading any further. An embedded stud within the component then pushes the guide portion, which detaches and is removed. Therefore, in order for this separately molded mating device to be properly inserted within the housing, elements such as the guide and the threaded portion are needed, which renders the device complex with multiple parts that also can increase the cost. Additionally, because the three separate elements must be simultaneously held in position, the process can be cumbersome and difficult. Furthermore, because the separately molded component threadingly engages the metallic lug, the metallic lug necessarily has a threaded aperture, thereby increasing the diameter of the aperture and hence decreasing the amount of metal in the metallic lug surrounding the bolt. The thread is typically large, about 15/16″-9, thereby eliminating a significant section of the current-carrying area between the lug and the mating diameter which is about 1¼ inches. In addition, because the mating device is a separately molded component, it suffers from some of the same problems of the other prior art devices discussed above.
In order to provide a better understanding of the state of the art related to the field of electrical termination systems, discussed below are several references. Although these references serve to provide a perspective as to the state of the related art, they fail to disclose the novel aspects of the present invention as discussed in detail herein and claimed hereafter.
For example, U.S. Pat. No. 5,114,357 to Luzzi (“Luzzi”) discloses a termination system for connecting a high voltage electrical cable to a high voltage electrical terminal. The housing of Luzzi can be generally L-shaped, having a cable receiving leg and a terminal receiving leg, wherein the terminal receiving leg has two bores. A bolt is captivated within the terminal receiving leg, and is operated by an external tool to join or separate a cable inserted in the cable receiving leg to a terminal inserted in a first bore of the terminal receiving leg. Luzzi discloses that the bolt can be within a second bore of the terminal receiving leg and include a cylindrical plug of hard insulating material to prevent the electricity from being conducted outside the connector through the second bore. The plug can be removed prior to tightening or loosening the bolt, and reinserted afterward in order to insulate the connector. Luzzi, however, does not disclose how to connect the termination system to a second device via the second bore, but is directed to an elbow having an insulating plug at the second bore. Furthermore, Luzzi does not provide for safety testing or grounding.
U.S. Pat. No. 3,883,208 Sankey et al. (“Sankey”) discloses a visible break tee connector for electrically connecting a high voltage cable to a terminal, comprising a T-shaped housing, a connecting member and a contact assembly. When installed, the connecting member is electrically connected to the terminal and the high voltage cable. The contact assembly is in electrical contact with the connecting member, providing a ground contact on disconnection. During disconnection, the housing, the connecting member and the contact assembly can be disconnected from the terminal without disconnecting the cable from the connecting member. Sankey, however, does not include a movable piston and therefore does not have loadbreak capabilities for safety testing or a fault close capability for safe grounding of the system. Accordingly, the elbow or cap connected to the opposite side of the first mating device cannot be removed when the cable is live without potentially causing an explosion in the termination system. This can be especially problematic because the termination system can provide a perception that the device does have loadbreak and fault close capabilities. Furthermore, if a cap was the mating part and was successfully removed, there is no safe way to ground the assembly without load break components inside the LRTP.
Sankey also requires unconventional products. For example, Sankey discloses the use of a specialized lug having a groove to house a conductive ring to electrically connect the cable to the connecting member. This also can hinder current flow between the cable and the connecting member, and therefore the terminal. Furthermore, the contact assembly is directly inserted into the housing through a passage, which produces a risk of contaminating the inside bore of the device which can lead to product failure.
Additionally, the prior art devices, because they require separated molded components, can result in an undesirably long stack height after assembly because of the interfaces of each element, such as the interface of the elbow in combination with the interface of the separately molded component.
In light of the prior art discussed herein, it is desirable to provide a simple, safe, easy to install, cable termination system having a reduced stack height suitable for use with devices known in the art.